A photonic phased array antenna may be used as a light source of scanning a photonic beam for image scanning in an autonomous car or robot. The photonic phased array antenna for application to various sectors is usually preferred to have the functionality of small size, high efficiency of photonic beam radiation, clear beam formation, and wide beam scanning range. For miniaturization of various requirements for the functionality, there is a need for a configuration of a photonic phased array antenna structure based on a semiconductor material. Further, since the efficiency of photonic beam radiation, visibility, and scanning functions are highly dependent on a structure of photonic radiator, it is required to propose a practical structure of photonic radiator based on a semiconductor material.
A semiconductor material includes a silicon or compound semiconductor, a metallic thin film material, and a dielectric material such as silicon nitride or silicon oxide which is used for manufacturing photonic devices made of the silicon or compound semiconductor.
A foregoing invention (US Patent Application No. 2014/0192394 A1) about a nanophotonics-based photonic phased array antenna has proposed a photonic phased array antenna where a phase-controlled photonic device is integrated in a form of M×M matrix based on a semiconductor silicon material.
In the foregoing invention, while the photonic radiator (corresponding to the antenna element in this specification thereof) is formed of a grating structure, photonic radiators are arranged in a form of matrix, and directional couplers and optical delay lines are arranged between unit photonic radiators. As such, because devices with different functions are crowded in one unit cell, a space occupied by a grating structure of the photonic radiator becomes smaller and thereby the dimension of gratings accommodated in such a small space should be scaled down in the dimension of several μm. Accordingly, if a scale of grating becomes smaller, it is difficult to obtain a high-performance beam because radiation efficiency of light wave is degraded.
A foregoing invention (PCT/KR2015/012199) made by the laboratory for the present application has proposed a phased array antenna capable of providing a photonic radiator part with a sufficient space as shown in FIG. 1. In FIG. 1, major elements forming the phased array antenna are roughly organized of a light source 100, photonic power distributors 101-1 and 101-2, phase controllers 102, and photonic radiators 104. Waveguides 106 are connected between the elements. Additionally, the waveguide 106 is also connected between the phase controllers 102 and the photonic radiators 104. Since high density of the waveguide could generate a coupling effect between the waveguides, their arrangement is important and for the reason, the waveguide is divided into phase-feeding lines 103.
The phased array of FIG. 1 is characterized, for the purpose of securing a sufficient space in a longitudinal direction of the photonic radiator 104, in that the power distributors 101-1 and 101-2, the phase controllers 102, and the phase-feeding lines 103 are arranged out of a 1×M radiator array 105. As such, the foregoing invention proposed that it is possible to secure a sufficient space between adjacent 1×M radiator arrays, as well as achieving a two-dimensional (2D) beam scanning function, by implementing a (1×M)×N phased array by independently arranging N-numbered 1×M radiator arrays up and down.
Accordingly, the following embodiments propose a photonic radiator structure which sufficiently uses a space in a longitudinal direction of a rating structure suitable for such a (1×M)×N phased array.